The lack of interaction between temafloxacin and combined oral contraceptive steroids

Drug interactions between non-rifamycin antibiotics and hormonal contraception: a systematic review

OBJECTIVE

The purpose of this study was to determine whether interactions between non-rifamycin antibiotics and hormonal contraceptives result in decreased effectiveness or increased toxicity of either therapy.

STUDY DESIGN

We searched MEDLINE, Embase, clinicaltrials.gov, and Cochrane libraries from database inception through June 2016. We included trials, cohort, case-control, and pharmacokinetic studies in any language that addressed pregnancy rates, pharmacodynamics, or pharmacokinetic outcomes when any hormonal contraceptive and non-rifamycin antibiotic were administered together vs apart. Of 7291 original records that were identified, 29 met criteria for inclusion.

STUDY APPRAISAL AND SYNTHESIS METHODS

Two authors independently assessed study quality and risk of bias using the United States Preventive Services Task Force evidence grading system. Findings were tabulated by drug class.

RESULTS

Study quality ranged from good to poor and addressed only oral contraceptive pills, emergency contraception pills, and the combined vaginal ring. Two studies demonstrated no difference in pregnancy rates in women who used oral contraceptives with and without non-rifamycin antibiotics. No differences in ovulation suppression or breakthrough bleeding were observed in any study that combined hormonal contraceptives with any antibiotic. No significant decreases in any progestin pharmacokinetic parameter occurred during co-administration with any antibiotic. Ethinyl estradiol area under the curve decreased when administered with dirithromycin, but no other drug.

CONCLUSION

Evidence from clinical and pharmacokinetic outcomes studies does not support the existence of drug interactions between hormonal contraception and non-rifamycin antibiotics. Data are limited by low quantity and quality for some drug classes. Most women can expect no reduction in hormonal contraceptive effect with the concurrent use of non-rifamycin antibiotics.

A comprehensive in vitro and in silico analysis of antibiotics that activate pregnane X receptor and induce CYP3A4 in liver and intestine

We have investigated several in silico and in vitro methods to improve our ability to predict potential drug interactions of antibiotics. Our focus was to identify those antibiotics that activate pregnane X receptor (PXR) and induce CYP3A4 in human hepatocytes and intestinal cells. Human PXR activation was screened using reporter assays in HepG2 cells, kinetic measurements of PXR activation were made in DPX-2 cells, and induction of CYP3A4 expression and activity was verified by quantitative polymerase chain reaction, immunoblotting, and testosterone 6beta-hydroxylation in primary human hepatocytes and LS180 cells. We found that in HepG2 cells CYP3A4 transcription was activated strongly (> 10-fold) by rifampin and troleandomycin; moderately (> or = 7-fold) by dicloxacillin, tetracycline, clindamycin, griseofulvin, and (> or = 4-fold) erythromycin; and weakly (> 2.4-fold) by nafcillin, cefaclor, sulfisoxazole, and (> 2-fold) cefadroxil and penicillin V. Similar although not identical results were obtained in DPX-2 cells. CYP3A4 mRNA and protein expression were induced by these antibiotics to differing extents in both liver and intestinal cells. CYP3A4 activity was significantly increased by rifampin (9.7-fold), nafcillin and dicloxacillin (5.9-fold), and weakly induced (2-fold) by tetracycline, sufisoxazole, troleandomycin, and clindamycin. Multiple pharmacophore models and docking indicated a good fit for dicloxacillin and nafcillin in PXR. These results suggest that in vitro and in silico methods can help to prioritize and identify antibiotics that are most likely to reduce exposures of medications (such as oral contraceptive agents) which interact with enzymes and transporters regulated by PXR. In summary, nafcillin, dicloxacillin, cephradine, tetracycline, sulfixoxazole, erythromycin, clindamycin, and griseofulvin exhibit a clear propensity to induce CYP3A4 and warrant further clinical investigation.

FFPRHC Guidance (October 2003): First Prescription of Combined Oral Contraception

The Guidance provides information for clinicians on the steps to be taken before providing a woman with her first prescription for combined oral contraception. It updates and replaces previous Faculty Guidance. A key to the grades of recommendations, based on levels of evidence, is given at the end of this document. Details of the methods used by the Clinical Effectiveness Unit (CEU) in developing this Guidance, and evidence tables summarising the research basis of the recommendations, are available on the Faculty website (www.ffprhc.org.uk). Abbreviations used include: blood pressure (BP), body mass (BMI), bone mineral density (BMD), breakthrough bleeding (BTB), British National Formulary (BNF), combined oral contraception (COC), Committee on Safety of Medicines (CSM), confidence interval (CI), deep vein thrombosis (DVT), emergency contraception (EC), ethinyl oestradiol (EE), Faculty Aid to Continuing Professional Development Topics (FACT), Family Planning Association (fpa), follicule-stimulating homone (FSH), general practitioner (GP), intermenstrual bleeding (IMB), luteinising hormone (LT), microgram, myocardial infarction (MI), odds ratio (OR), oral contraception (OC), pulmonary embolism (PE), relative risk (RR), Scottish Intercollegiate Guideline Network (SIGN), sexually transmitted infection (STI), Summary of Product Characteristics (SPCs), venous thomboembolism (VTE), World Health Organization (WHO), WHO Medical Eligibility Criteria (WHOMEC), WHO Selected Practice Recommendations (WHOSPR).

Antibiotics and oral contraceptives

With the exception of rifampin-like drugs, there is a lack of scientific evidence supporting the ability of commonly prescribed antibiotics, including all those routinely employed in outpatient dentistry, to either reduce blood levels and/or the effectiveness of oral contraceptives. To date, all clinical trials studying the effects of concomitant antibiotic therapy (with the exception of rifampin and rifabutin) have failed to demonstrate an interaction. Like all drugs, oral contraceptives are not 100% effective with the failure rate in the typical United States population reported to be as high as 3%. It is thus possible that the case reports of unintended pregnancies during antibiotic therapy may simply represent the normal failure rate of these drugs. Considering that both drug classes are prescribed frequently to women of childbearing potential, one would expect a much higher rate of oral contraceptive failure in this group of patients if a true drug:drug interaction existed. On the other hand, if the interaction does exist but is a relatively rare event, occurring in, say, 1 in 5000 women, clinical studies such as those described in this article would not detect the interaction. The pharmacokinetic studies of simultaneous antibiotic and oral contraceptive ingestion, and the retrospective studies of pregnancy rates among oral contraceptive users exposed to antibiotics, all suffer from one potential common weakness, i.e., their relatively small sample size. Sample sizes in the pharmacokinetic trials ranged from 7 to 24 participants, whereas the largest retrospective study of pregnancy rates still evaluated less than 800 total contraceptive users. Still, the incidence of such a rare interaction would not differ from the accepted normal failure rate of oral contraceptive therapy. The medico-legal ramifications of what looks like at best a rare interaction remains somewhat "murky." On one hand, we have medico-legal experts advising the profession to exercise caution and warn all oral contraceptive users of a potential reduction in efficacy during antibiotic therapy. These opinions are not evidence-based and rely heavily on one or two legal proceedings that cannot even be substantiated. On the other hand, there is one recently published legal proceeding in which the outcome was in favor of the oral surgeon. There is clearly a need for additional scientific research in oral contraceptive users that incorporates larger sample sizes, different time courses (prophylactic use versus standard 7-10 day use versus extended use), and different delivery systems (systemic administration versus local-controlled delivery) of antibiotic therapy. Though experts on this topic still recommend informing oral contraceptive users of the potential for a rare interaction, and for clinicians to advise them to employ additional barrier techniques of birth control during antibiotic therapy and for at least 1 week beyond the last dose [40], it is hoped that a set of guidelines regarding this controversy will eventually be published that is evidence-based, and not solely the results of anecdotal reports, expert opinions, and legal proceedings.

Efficacy of a low-dose oral contraceptive containing 20 microg of ethinyl estradiol and 100 microg of levonorgestrel for the treatment of moderate acne: A randomized, placebo-controlled trial

BACKGROUND

Acne is a multifactorial disease in which androgens appear to play an important role. A low-dose oral contraceptive containing 20 microg of ethinyl estradiol and 100 microg of levonorgestrel (EE/LNG) has been shown to improve biochemical markers of androgenicity. Lowering bioavailable androgens may improve acne.

OBJECTIVE

The aim of this study was to evaluate the efficacy and safety of a low-dose oral contraceptive containing 20 microg of EE and 100 microg of LNG for the treatment of moderate acne.

METHODS

In a randomized, double-blind, placebo-controlled clinical trial, healthy female subjects (n = 371; >/=14 years old) with regular menstrual cycles and moderate facial acne were randomly assigned to receive EE/LNG or placebo for 6 cycles of 28 days. Acne lesion counts and clinician global assessment were performed at the end of each cycle. Patient self-assessments were collected and biochemical markers of androgenicity were also measured.

RESULTS

At the end of the study, the number of inflammatory and total lesions was significantly lower with EE/LNG compared with placebo (P <.05). Patients in the EE/LNG group also had significantly better scores for clinician global and patient self-assessments than those in the placebo group (P <.05). Biochemical markers of androgenicity improved during EE/LNG treatment compared with placebo and baseline values.

CONCLUSION

A low-dose oral contraceptive containing EE/LNG is effective and safe for the treatment of moderate acne.

Oral contraceptives as anti-androgenic treatment of acne

Although acne is seldom associated with high serum levels of androgens, it has been shown that female acne patients have definite increases in ovarian and adrenal androgen levels when compared to appropriate controls. As shown in several pilot and in multiple open and comparative studies, oral contraceptives (OCs) are effective in causing a significant regression of mild to moderate acne. These results have been confirmed by multicentre randomized trials where low-dose OCs did not cause side effects different from those of the placebo-controlled group. The beneficial effect of OCs is related to a decrease in ovarian and adrenal androgen precursors; to an increase in sex hormone-binding globulin (SHBG), which limits free testosterone; and to a decrease in 3a-androstenediol glucuronide conjugate, the catabolite of dihydrotestosterone (DHT) formed in peripheral tissues. The estrogen-progestin combination containing cyproterone acetate (CPA) is particularly effective in treating acne, since this progestin also has a direct peripheral anti-androgenic action in blocking the androgen receptor. Only two open studies and one randomized study on small numbers of patients have reported some efficacy of spironolactone used alone or in combination with an OC in the treatment of acne. The new non-steroidal anti-androgens flutamide and finasteride are being evaluated for the treatment of hirsutism. Oral antibiotics are prescribed to patients with inflammatory lesions, where they are effective in decreasing the activity of microbes, the activity of microbial enzymes, and leukocyte chemotaxis. Concomitant intake of an OC and an antibiotic usually prescribed for acne does not impair the contraceptive efficacy of the OC. A second effective contraceptive method should be used whenever there would be decreased absorption or efficacy of the OC (digestive problems, breakthrough bleeding), lack of compliance and use of a type or dose of antibiotic different from that usually prescribed for acne.Overall, the various approaches for the treatment of acne depend on the needs of the patient and on the therapeutic objectives. Low-dose OCs are effective in improving acne and have side effects similar to placebo. They can be used alone or in combination with other anti-acne agents. The physician prescribing an OC as an anti-androgen intervention should take into account the multiple factors involved in acne and be familiar with current non-hormonal agents for treating mild to moderate acne. Individuals presenting with moderate to severe acne, or not responding to an estrogen-progestin combination, should be referred to a dermatologist.

Oral contraceptive efficacy and antibiotic interaction: a myth debunked

The purpose of this study was to review the pharmacokinetic and clinical literature regarding the efficacy of oral contraceptives when used concomitantly with antibiotic therapy. Relevant literature was identified by searching MEDLINE and EMBASE. Other sources were located by consulting the bibliographies of the material collected from MEDLINE and EMBASE. Pharmacokinetic evidence demonstrates that plasma levels of oral contraceptive steroids are unchanged with the concomitant administration of antibiotics, including ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline. However, reduced steroid levels have been reported in women taking rifampin with oral contraceptives. Clinical reports of contraceptive failure with antibiotic use are retrospective, have multiple potential biases, and are not supported by pharmacokinetic data. Available scientific and pharmacokinetic data do not support the hypothesis that antibiotics (with the exception of rifampin) lower the contraceptive efficacy of oral contraceptives.

Interaction between broad-spectrum antibiotics and the combined oral contraceptive pill. A literature review

There is considerable variation in opinion about the importance of drug interactions between the combined oral contraceptive pill (COCP) and broad-spectrum antibiotics. Clinical practice varies widely, especially between doctors in Europe and those in the US. Rifampicin and griseofulvin induce hepatic enzymes and do appear to have a genuine interaction with the COCP, leading to reduced efficacy. The situation with the broad-spectrum antibiotics is less clear. There are relatively few prospective studies of the pharmacokinetics of concurrent COCP and antibiotic use and few, if any, demonstrate a convincing basis for any reduced contraceptive efficacy. There is evidence, however, that variable contraceptive steroid handling could make some women, at some times, more susceptible to COCP failure. Given the serious consequences of unwanted pregnancy, the cautious approach of using additional or alternative contraception during short courses of broad-spectrum antibiotics and the initial weeks of long-term antibiotic administration may be justified to safeguard the few unidentifiable women who may be at risk. Conflicting opinion and advice is potentially confusing to both professionals and patients, and instructions for additional precautions during and after concurrent COCP and antibiotic use are complicated. Many women are ignorant of, or confused about, the circumstances that can cause OC to fail. Health professionals who prescribe the COCP must continue to strive to educate women about the mode of action and about the times when there is the greatest danger of failure. Professionals who feel that concurrent antibiotic use represents a real threat to contraceptive efficacy of the COCP should be prepared to present the advice for additional contraceptive precautions in a simple and consistent way, backed up with written information and reinforced at regular intervals.

Adverse drug interactions in dental practice: interactions involving antibiotics. Part II of a series

BACKGROUND

The prudent use of antibiotics is an integral part of dental practice. While these agents generally are considered safe in the dental setting, their use can result in interactions that can lead to serious morbidity in dental patients.

METHODS

The faculty of a symposium entitled "Adverse Drug Interactions in Dentistry: Separating the Myths From the Facts" did an extensive literature review on drug interactions. Through this, they were able to establish a significance rating of alleged adverse drug interactions as they relate to dentistry, based on their scientific documentation and severity of effect. The author of this article focused on antibiotics.

RESULTS

Most of the reported drug interactions discussed in this article are well-documented by clinical studies. It is particularly important that dentists be aware of the potentially serious and life-threatening interactions of the antibiotics erythromycin, clarithromycin and metronidazole, and of the antifungal agents ketoconazole and itraconazole, with a host of other drugs whose metabolism is impaired by these antimicrobial agents. In contrast, the alleged ability of commonly employed antibiotics to reduce the effectiveness of oral contraceptive agents is not adequately supported by clinical research. It still is recommended, however, that clinicians discuss this possible interaction with their patients, as it might represent a relatively rare event that cannot be discerned in clinical trials.

CONCLUSIONS

Potentially serious adverse drug interactions can occur between antimicrobial agents used in dental practice and other drugs patients are taking for a variety of medical conditions.

CLINICAL IMPLICATIONS

It is important that dentists stay abreast of potential drug interactions involving antibiotics to avoid serious morbidity among their patients.

Risk for ovulation in women taking a low-dose oral contraceptive (Microgynon) when receiving antibacterial treatment with a fluoroquinolone (ofloxacin)

The possibility of escape ovulation in women using a fluoroquinolone ofloxacin for antibacterial treatment at a dose of 200 mg twice daily for 7 days when taking a combined oral contraceptive (Microgynon, 150 micrograms levonorgestrel and 30 micrograms ethinyl estradiol) was studied in 20 women. By using a placebo-controlled, randomized, cross-over design 6 contraceptive pill cycles were followed. Follicle-stimulating hormone and estradiol concentrations were measured on tablet days 5-8, 19-21; progesterone was assayed on days 19-21 during treatment with ofloxacin or placebo. Ultrasonographical investigations for measurements of the number and diameter of ovarian follicles were performed on one of days 5-10, 11-17, 18-24, 25-28. No indications of ovulation during ofloxacin medication were detected. It is concluded that alternative contraceptive precautions should not be needed when ofloxacin is prescribed for patients taking oral contraceptives.

Effects of temafloxacin and ciprofloxacin on the pharmacokinetics of caffeine

A number of quinolone antibacterial agents, particularly enoxacin, pefloxacin, pipemidic acid and ciprofloxacin, are known to decrease the clearance of methylxanthines. The effects of temafloxacin and ciprofloxacin on the pharmacokinetics of caffeine were therefore compared in a 3-way crossover study in 12 healthy young volunteers. Each volunteer received 183mg once-daily doses of caffeine in conjunction with twice-daily placebo, temafloxacin 600mg and ciprofloxacin 750mg in 3 separate phases according to a randomised sequence. A doubling of the area under the plasma concentration-time curve (77.8 vs 31.8 mg/L.h) and terminal-phase half-life (9.7 vs 4.5h) of caffeine were observed in the presence of ciprofloxacin. The magnitude of the reduction in the intrinsic clearance of caffeine produced by ciprofloxacin was greater than that described in the literature for ciprofloxacin and theophylline. This may partly be explained by intertrial differences in dosage and study design. Coadministration of temafloxacin did not have any effect on the pharmacokinetics of caffeine, confirming results of other studies suggesting that this agent does not affect methylxanthine clearance. Accordingly, it appears that restriction of caffeine intake during temafloxacin therapy is not necessary.